Molecular acidity: A quantitative conceptual density functional theory description.

Area of Science:

• Computational Chemistry
• Physical Chemistry
• Quantum Chemistry

Background:

• Accurate prediction of molecular acidity (pKa) remains a significant challenge in computational chemistry.
• Existing methods often rely on complex calculations or approximations.

Purpose of the Study:

• To reformulate relationships between electronic/reactivity properties and pKa values using conceptual density functional theory.
• To compare this new approach with the established thermodynamic cycle method for predicting pKa.

Main Methods:

• Utilized molecular electrostatic potential (MEP) on the nucleus and sum of valence natural atomic orbital (NAO) energies.
• Applied conceptual density functional theory to reformulate existing relationships.
• Tested the approach on 27 main group and transition metal-water complexes.

Main Results:

• Demonstrated strong linear correlations between MEP and NAO properties of the dissociating proton and experimental pKa data.
• Showed that the reformulated relationships are consistent with the thermodynamic cycle method.
• Achieved statistically similar accuracy compared to the conventional thermodynamic cycle method.

Conclusions:

• The proposed method based on MEP and NAO properties offers a robust and accurate way to estimate pKa values.
• This approach provides a computationally efficient alternative to the thermodynamic cycle method for predicting molecular acidity.